A graphene lithium calcium-polyurea-based grease and its preparation method and application

Abstract

The present invention provides a kind of graphene lithium calcium polyurea grease and its preparation method and application, the graphene lithium calcium polyurea grease includes the following components in parts by mass: base oil 80 98 parts, calcium lithium thickener 1 10 parts, polyurea thickener 0.5 8 parts, composite graphene 0.001 5 parts, additive 2 12 parts;The composite graphene includes a combination of at least two of modified graphene oxide, ionic liquid modified graphene, and three-dimensional structure graphene. The present invention is compounded with base oil and calcium lithium thickener, polyurea thickener, composite graphene and additives, so that while having excellent colloidal stability, mechanical stability, water resistance, anti-shear performance, it also has excellent extreme pressure and wear resistance, high temperature resistance and low temperature performance, so that it fully meets the various working conditions requirements of heavy machinery industry.

Description

Technical Field

[0001] The present invention belongs to the technical field of lubricating oils, and in particular relates to a graphene lithium calcium-polyurea-based grease and a preparation method and application thereof. Background Art

[0002] Lubricants play a vital role in industrial production. Used in the frictional areas of mechanical equipment, they reduce friction, thereby minimizing unnecessary energy loss, protecting machinery, and extending its service life. Grease, a thick, oily substance, is a commonly used lubricant. It not only lubricates and reduces friction, but also seals, fills gaps, and protects metals.

[0003] Among currently available greases, lithium-based greases offer superior overall performance, including excellent high-temperature resistance, shear resistance, water resistance, a long lubrication life, and a wide temperature range. However, significant price increases in the lithium mining industry in recent years have impacted the price of lithium hydroxide, the primary raw material for lithium-based grease production, and have led to a shortage of supply. This has significantly impacted the production and application of these greases, necessitating the development of alternatives to lithium-based greases within the industry.

[0004] Calcium resources are widely available and abundant. Calcium-based greases made from calcium-based greases are low-cost, exhibit excellent water resistance, mechanical stability, and colloidal stability. However, calcium-based greases have a low dropping point, insufficient high-temperature resistance, and poor extreme pressure and anti-wear properties. Polyurea greases are another type of lithium-free, lower-cost grease. Polyurea thickeners are the addition reaction product of isocyanates and organic amines. They offer advantages such as good high-temperature performance and a high dropping point, as well as excellent shear resistance and lubrication life. However, they suffer from poor water resistance and extreme pressure and anti-wear properties. Currently, the industry is experimenting with combining calcium-based greases with polyurea greases to balance their performance characteristics. For example, CN115247094A discloses a polyurea-anhydrous calcium-based grease, which is composed of anhydrous calcium-based grease and urea-based grease, wherein the anhydrous calcium-based grease includes a thickener A, a base oil, a rust inhibitor and an antioxidant, and the thickener A is prepared from calcium hydroxide, stearic acid and 12-hydroxystearic acid; the urea-based grease includes a thickener B, a base oil, a rust inhibitor and an antioxidant, and the thickener B is prepared from MDI, a fatty amine and an alicyclic amine; although the polyurea-anhydrous calcium-based grease achieves a good balance in high temperature resistance, water resistance, shear resistance and mechanical stability, and has a performance level comparable to that of lithium-based grease, it still has obvious deficiencies in extreme pressure and anti-wear performance.

[0005] Adding solid anti-wear additives is one of the effective methods to improve the anti-wear properties of grease. Currently disclosed solid anti-wear additives include graphite, molybdenum disulfide, boron nitride, graphene, etc. Among them, graphene is a new material with a single-layer sheet structure composed of carbon atoms. It is the thinnest and hardest nanomaterial known to date. Graphene material is a carbon nanomaterial composed of stacked graphene layers with no more than 10 layers. A large number of studies on the tribological properties of graphene materials have shown that graphene materials have excellent lubrication and anti-wear properties, and have therefore become potential high-performance lubricating materials. However, graphene materials are difficult to evenly disperse in grease base oils, which greatly restricts their application in greases.

[0006] To address the dispersibility problem of graphene materials, attempts have been made to modify graphene. For example, CN107739643A discloses a method for preparing a lubricant containing a surface-modified carbon nanomaterial. The method comprises: reacting graphene with dopamine hydrochloride under certain conditions to obtain a graphene nanomaterial coated with polydopamine; then treating the graphene nanomaterial with an alkylamine to obtain a modified graphene nanomaterial coated with polydopamine and grafted with a long carbon chain alkane; and preparing modified carbon nanotubes and modified carbon nanofibers using a similar method. The modified graphene nanomaterial, modified carbon nanotubes, and modified carbon nanofibers are then mixed with a base oil and other additives to obtain a lubricant containing the surface-modified carbon nanomaterial. The graphene material has good dispersibility in the base oil. However, the product suffers from insufficient dispersion stability after long-term storage, and its extreme pressure, anti-wear, and high and low temperature performance cannot meet the performance requirements of the heavy machinery industry.

[0007] Therefore, developing a grease with high extreme pressure and wear resistance, good temperature resistance, and good dispersion of graphene materials is an urgent problem to be solved in this field. Summary of the Invention

[0008] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a graphene lithium calcium-polyurea based grease and its preparation method and application. By compounding the base oil with a calcium lithium-based thickener, a polyurea thickener, a composite graphene and additives, the graphene in the system has excellent dispersibility and stability. The graphene lithium calcium-polyurea based grease has excellent extreme pressure and anti-wear properties, high temperature resistance and low temperature performance, and can fully meet the working conditions required for application in the heavy machinery industry.

[0009] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a graphene lithium calcium-polyurea-based grease, wherein the graphene lithium calcium-polyurea-based grease comprises the following components in parts by mass:

[0011]

[0012] The composite graphene includes a combination of at least two of modified graphene oxide, ionic liquid modified graphene, and three-dimensional structured graphene.

[0013] The graphene lithium calcium-polyurea grease provided by the present invention uses a combination of a calcium lithium-based thickener and a polyurea thickener as the thickener. This combines the performance characteristics of calcium, lithium, and polyurea, resulting in excellent colloidal stability, mechanical stability, high temperature resistance, water shock resistance, and the like, while reducing raw material costs. Furthermore, the composite graphene exhibits excellent dispersibility and stability in a system of base oil, calcium lithium-based thickener, and polyurea thickener, thereby enabling the graphene's performance advantages in lubrication and anti-wear to be maximized. Furthermore, the ionic liquid modified in the composite graphene synergizes with the base oil, calcium lithium-based thickener, and polyurea thickener to further improve high-temperature resistance and low-temperature performance. Therefore, the present invention compounds the base oil with a calcium-lithium-based thickener, a polyurea thickener, composite graphene, and additives, so that the graphene lithium calcium-polyurea-based grease has excellent colloidal stability, mechanical stability, water resistance, and shear resistance, as well as excellent extreme pressure and wear resistance, high temperature resistance, and low temperature performance. In particular, significant improvements are achieved in extreme pressure and wear resistance and low temperature performance, fully meeting the application requirements of the heavy machinery industry under special working conditions (such as extreme low temperatures).

[0014] The composite graphene of the present invention comprises a combination of at least two of modified graphene oxide, ionic liquid modified graphene, and three-dimensional structured graphene, wherein the modified graphene oxide has good dispersion stability and can maintain a continuous and uniform dispersion of graphene in the grease to prevent graphene agglomeration and accumulation, thereby exerting the most favorable friction reduction and anti-wear effect. The ionic liquid modified graphene not only ensures long-term dispersion stability, but also has excellent temperature resistance and excellent anti-wear performance. While improving the anti-wear performance of the grease, it can also expand its operating temperature range. The three-dimensional structured graphene has a stronger wrapping property for the base oil and can exert a sponge effect, so that the grease has the characteristics of high temperature resistance and significant extreme pressure and anti-wear effects. The present invention compounds at least two of the modified graphene oxide, ionic liquid modified graphene, and three-dimensional structured graphene as a composite graphene, so that the graphene material is uniformly dispersed in the grease system, with excellent dispersion stability, and imparts excellent friction reduction and anti-wear performance and high and low temperature resistance to the graphene lithium calcium-polyurea-based grease.

[0015] Among them, the mass parts of the base oil are 80-98 parts, for example, it can be 81 parts, 82 parts, 83 parts, 84 parts, 85 parts, 86 parts, 87 parts, 88 parts, 89 parts, 90 parts, 92 parts, 95 parts or 97 parts, as well as specific point values ​​between the above points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range, preferably 83-95 parts.

[0016] The mass fraction of the calcium-lithium-based thickener is 1-10 parts, for example, it can be 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 8.5 parts, 9 parts or 9.5 parts, as well as specific values ​​between the above points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific points included in the range, preferably 4-6 parts.

[0017] The mass fraction of the polyurea thickener is 0.5-8 parts, for example, it can be 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts or 7.5 parts, as well as specific values ​​between the above points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific points included in the range, preferably 1-4 parts.

[0018] The mass fraction of the composite graphene is 0.001-5 parts, for example, it can be 0.005 parts, 0.01 parts, 0.05 parts, 0.1 parts, 0.3 parts, 0.5 parts, 0.8 parts, 1 parts, 1.2 parts, 1.4 parts, 1.5 parts, 1.8 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts or 4.5 parts, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range, preferably 0.01-3 parts.

[0019] The mass parts of the additive are 2-12 parts, for example, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts or 11 parts, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0020] Preferably, the base oil includes any one of mineral base oil, synthetic base oil, and plant base oil, or a combination of at least two of them.

[0021] Preferably, the mineral base oil includes paraffinic base oil and / or naphthenic base oil, illustratively including but not limited to: any one of 500SN, 350SN, 250SN, 150SN, 150BS, bran full three-line oil, 4010, or a combination of at least two thereof.

[0022] Preferably, the synthetic base oil includes any one of synthetic hydrocarbon oil, ether oil, and ester oil, or a combination of at least two of them.

[0023] Preferably, the calcium-lithium-based thickener comprises a combination of 12-hydroxy lithium stearate and 12-hydroxy calcium stearate.

[0024] Preferably, the mass ratio of the lithium 12-hydroxystearate to the calcium 12-hydroxystearate is 1:(0.05-15), for example, it can be 1:0.07, 1:0.1, 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2, 1:2.2, 1:2.5, 1:2.8, 1:3, 1:3.2, 1:3.5, 1:3.8, 1:4, 1:4.2, 1:4.5 1:4.8, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14 or 1:15, etc., more preferably 1:(0.5-5).

[0025] As a preferred technical solution of the present invention, the mass ratio of the lithium 12-hydroxystearate to the calcium 12-hydroxystearate is 1: (0.5-5). As a calcium lithium-based thickener, it is compounded with a polyurea thickener and combined with a base oil, composite graphene, and additives to give the graphene lithium calcium-polyurea-based grease excellent stability, high temperature resistance, water shock resistance, extreme pressure and wear resistance, high temperature resistance, and low temperature performance, while having a low production cost. If the amount of calcium 12-hydroxystearate is too high, it will affect the high temperature resistance and extreme pressure and wear resistance of the grease; if the amount of lithium 12-hydroxystearate is too high, it will increase the cost of raw materials.

[0026] In the present invention, the polyurea thickener may be a commercially available polyurea thickener, or may be prepared using isocyanate and polyamine compounds. The preparation method is a polyurea preparation method known in the art, and the present invention does not specifically limit it.

[0027] Preferably, the composite graphene includes a combination of modified graphene oxide, ionic liquid modified graphene and three-dimensional structured graphene.

[0028] Preferably, the mass percentage of the modified graphene oxide in the composite graphene is 70-95%, for example, it can be 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90%, 92% or 94%, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0029] Preferably, the mass percentage of the ionic liquid-modified graphene in the composite graphene is 5-15%, for example, 6%, 8%, 10%, 11%, 12%, 13% or 14%, and specific values ​​between the above points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific values ​​included in the range.

[0030] Preferably, the mass percentage of three-dimensional graphene in the composite graphene is 5-15%, for example, it can be 6%, 8%, 10%, 11%, 12%, 13% or 14%, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0031] Preferably, the modified graphene oxide is sulfonated modified graphene oxide grafted with long carbon chains.

[0032] Illustratively, the modified graphene oxide can be obtained by the method disclosed in 201580002367.X or 202010670619.9.

[0033] Preferably, the particle size of the three-dimensional graphene structure is 200-300nm, for example, it can be 210nm, 220nm, 230nm, 240nm, 250nm, 260nm, 270nm, 280nm or 290nm, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0034] Preferably, the specific surface area of ​​the three-dimensional graphene is 1200-1500m 2 / g, for example, it can be 1220m 2 / g、1250m 2 / g、1280m 2 / g、1300m 2 / g、1320m 2 / g、1350m 2 / g、1380m 2 / g、1400m 2 / g、1420m 2 / g、1450m 2 / g or 1480m 2 / g, and specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range. 1260-1450m 2 / g.

[0035] Preferably, the electrical conductivity of the three-dimensional graphene structure is 1600-1900 S / m, for example, it can be 1650 S / m, 1700 S / m, 1750 S / m, 1800 S / m or 1850 S / m, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0036] Exemplarily, the three-dimensional graphene structure can be prepared by the method disclosed in CN108423665A; or can be prepared by the following method; preferably, the method shown below is used to compound the three-dimensional graphene structure with other graphene to obtain a grease with better performance.

[0037] Preferably, the three-dimensional graphene is prepared by the following method, which includes: mixing a fumaric acid aqueous solution with a macroporous weakly acidic cation exchange resin and performing a first treatment, drying, and obtaining a fumaric acid / ion exchange resin; performing a second treatment on the fumaric acid / ion exchange resin in a KOH aqueous solution, drying, and crushing it using a disintegrator to obtain a crushed product; performing high-temperature cracking on the crushed product, and then washing it with acid, water, and alcohol, and drying to obtain the three-dimensional graphene.

[0038] Preferably, the time for the first treatment and the second treatment is independently 2-12 hours, for example, it can be 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours or 11 hours, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0039] Preferably, the temperature of the high-temperature cracking is 700-900°C, for example, it can be 720°C, 750°C, 780°C, 800°C, 820°C, 850°C or 880°C, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0040] Preferably, the high temperature cracking time is 2-8h, for example, it can be 3h, 4h, 5h, 6h or 7h, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0041] Preferably, the ionic liquid in the ionic liquid-modified graphene includes an imidazole ionic liquid.

[0042] Preferably, the imidazolium ionic liquid includes any one of 1-butyl-2-methylimidazolium tetrafluoroborate, 1-butyl-2-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-2,3-dimethylimidazolium tetrafluoroborate, and 1-butyl-2,3-dimethylimidazolium hexafluorophosphate, or a combination of at least two thereof.

[0043] Preferably, the ionic liquid modified graphene is prepared by the following method, which comprises:

[0044] Electrochemical stripping is performed using graphite as an electrode and an ionic liquid aqueous solution as an electrolyte to obtain a modified graphene dispersion; and the modified graphene dispersion is centrifuged to obtain the ionic liquid-modified graphene.

[0045] Preferably, the ionic liquid aqueous solution is an imidazole ionic liquid aqueous solution.

[0046] As a preferred technical solution of the present invention, the ionic liquid-modified graphene is prepared by electrochemical exfoliation technology. During the electrochemical exfoliation of graphite, an electric potential is applied to the main graphite electrode, and the current drives ions or charged molecules to migrate into the graphite interlayer wall, causing the graphite structure to expand and then peel off into graphene; at the same time, an imidazole ionic liquid aqueous solution is used as an electrolyte. The process of graphite exfoliation to form graphene is accompanied by chemical modification of the graphene by the imidazole ionic liquid, realizing the interlayer intercalation and grafting modification of the graphene by the imidazole ionic liquid functional groups, so that the prepared ionic liquid-modified graphene has excellent dispersion uniformity and stability in the grease system of the present invention, thereby effectively improving its long-term dispersion stability and dispersion stability under complex / harsh conditions. The ionic liquid modified graphene, as one of the components of the composite graphene, works synergistically with the base oil, calcium lithium-based thickener and polyurea thickener to significantly improve the extreme pressure and anti-wear properties, high temperature resistance and low temperature performance of the graphene lithium calcium-polyurea-based grease, and broaden the operating temperature range of the grease.

[0047] Preferably, the present invention adopts an electrochemical exfoliation method to prepare ionic liquid-modified graphene, wherein both the positive electrode and the negative electrode are graphite electrodes, preferably graphite rods, and high-quality ionic liquid-modified graphene is prepared by controlling the magnitude of the pulsed DC voltage and the type of ionic liquid. This method consumes less chemical reagents, has low cost, simple equipment, easy operation, and is green and environmentally friendly.

[0048] Preferably, the volume ratio of the ionic liquid to water in the ionic liquid aqueous solution is 1:(2-10), for example, it can be 1:3, 1:4, 1:5, 1:6, 1:7, 1:8 or 1:9, and more preferably 1:(4-8).

[0049] Preferably, two graphite rods are used as cathode and anode, and are connected to a DC power supply to provide an operating voltage. When voltage is applied, the graphite rods begin to peel off layer by layer. As time goes by, the color of the electrolyte changes from light yellow to dark yellow, then to dark brown, and finally to a black solution with a precipitate, obtaining a dispersion containing ionic liquid-modified graphene. By designing a specific voltage, the size, morphology and functional modification degree of the graphene by the ionic liquid can be regulated to obtain the ionic liquid-modified graphene of different sizes, morphologies and functionalization degrees. Furthermore, by designing different centrifugal speeds, ionic liquid-modified graphene of different numbers and sizes of layers can be obtained, and as the centrifugal speed increases, the number of layers of the ionic liquid-modified graphene decreases.

[0050] Preferably, the voltage of the electrochemical stripping is 5-20V, for example, it can be 6V, 7V, 8V, 9V, 10V, 11V, 12V, 13V, 14V, 15V or 18V, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0051] Preferably, the electrochemical stripping time is 0.5-10h, for example, it can be 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h or 9h, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0052] Preferably, the rotation speed of the centrifugal separation is 4000-14000 rpm, for example, it can be 5000 rpm, 6000 rpm, 7000 rpm, 8000 rpm, 9000 rpm, 10000 rpm, 11000 rpm, 12000 rpm or 13000 rpm, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0053] Preferably, the centrifugal separation time is 1-30 min, for example, it can be 2 min, 5 min, 8 min, 10 min, 12 min, 15 min, 18 min, 20 min, 22 min, 25 min or 28 min, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0054] Preferably, the centrifugal separation further includes washing and drying steps.

[0055] Preferably, the washing reagent comprises ethanol and / or water.

[0056] Preferably, the additive includes any one of an extreme pressure anti-wear agent, an adhesive, a corrosion inhibitor, an antioxidant, and a rust inhibitor, or a combination of at least two thereof.

[0057] Preferably, the graphene lithium calcium-polyurea-based grease also includes 1-5 parts of extreme pressure anti-wear agent in parts by mass. The extreme pressure anti-wear agent can be 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts or 4.5 parts, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the said range.

[0058] Preferably, the extreme pressure anti-wear agent includes any one or a combination of at least two of a boron extreme pressure anti-wear agent, a sulfide extreme pressure anti-wear agent, a phosphorus extreme pressure anti-wear agent, and a chloride extreme pressure anti-wear agent, more preferably any one or a combination of at least two of a boron extreme pressure anti-wear agent, a sulfide extreme pressure anti-wear agent, and a chloride extreme pressure anti-wear agent, and even more preferably a combination of a boron extreme pressure anti-wear agent, a sulfide extreme pressure anti-wear agent, and a chloride extreme pressure anti-wear agent.

[0059] Preferably, the graphene lithium calcium-polyurea grease further includes 0.1-1.5 parts of an adhesive in parts by mass, and the adhesive may be 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 parts, 1.2 parts or 1.4 parts, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the said range.

[0060] Preferably, the adhesive comprises an OCP type tackifier.

[0061] Preferably, the graphene lithium calcium-polyurea grease further includes 0.1-1.5 parts of preservatives by mass, and the preservatives may be 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 parts, 1.2 parts or 1.4 parts, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the said range.

[0062] Preferably, the graphene lithium calcium-polyurea grease further includes 0.1-1.5 parts of antioxidant in parts by mass. For example, the antioxidant may be 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 parts, 1.2 parts or 1.4 parts, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the said range.

[0063] Preferably, the antioxidant comprises an amine antioxidant and / or a phenolic antioxidant.

[0064] Preferably, the graphene lithium calcium-polyurea grease further includes 0.1-1.5 parts of a rust inhibitor in parts by mass. The rust inhibitor may be 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 parts, 1.2 parts or 1.4 parts, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0065] Preferably, the rust inhibitor includes any one of calcium petroleum sulfonate, calcium isooctanoate, and zinc isooctanoate, or a combination of at least two of them.

[0066] Preferably, the graphene lithium calcium-polyurea grease also includes a dye, the mass portion of which is ≤1.5 parts, for example, it can be 0 (not added), 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 parts, 1.2 parts or 1.4 parts, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0067] In a second aspect, the present invention provides a method for preparing the graphene lithium calcium-polyurea grease as described in the first aspect, the preparation method comprising:

[0068] preparing a grease body comprising a base oil, a calcium-lithium thickener, and a polyurea thickener;

[0069] The composite graphene and additives are added to the grease body and blended to obtain the graphene lithium calcium-polyurea-based grease.

[0070] In the preparation method provided by the present invention, the composite graphene and additives are added in the blending stage to have better dispersibility and dispersion stability. The composite graphene includes a combination of at least two of modified graphene oxide, ionic liquid modified graphene, and three-dimensional structured graphene, and has better compatibility with other additives and better compounding with the grease system, thereby optimizing the high temperature resistance, low temperature resistance and extreme pressure and wear resistance of the graphene lithium calcium-polyurea-based grease.

[0071] Preferably, the preparation method of the grease body includes: mixing base oil, 12-hydroxystearic acid and a saponifier solution, performing a saponification reaction, adding a polyurea thickener thereto after dehydration for compounding, and then refining and homogenizing to obtain the grease body; the saponifier solution includes a combination of lithium hydroxide, calcium hydroxide and water.

[0072] Preferably, the mass ratio of the lithium hydroxide to the calcium hydroxide is 1:(0.4-9), for example, it can be 1:0.5, 1:0.8, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8 or 1:8.5, etc.

[0073] Preferably, the temperature of the saponification reaction is 90-120°C, for example, it can be 95°C, 100°C, 102°C, 105°C, 108°C, 110°C, 112°C, 115°C or 118°C, as well as specific values ​​between the above points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific points included in the range, and 100-110°C is further preferred.

[0074] Preferably, the saponification reaction time is 1-3 h, for example, it can be 1.2 h, 1.5 h, 1.8 h, 2 h, 2.2 h, 2.5 h or 2.8 h, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range, and 1.5-2.5 h is further preferred.

[0075] Preferably, the compounding temperature is 120-140°C, for example, it can be 122°C, 125°C, 128°C, 130°C, 132°C, 135°C or 138°C, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range, and 125-135°C is further preferred.

[0076] Preferably, the compounding time is 1-3h, for example, it can be 1.2h, 1.5h, 1.8h, 2h, 2.2h, 2.5h or 2.8h, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range, and 1.5-2.5h is further preferred.

[0077] Preferably, the refining temperature is 130-140°C, for example, it can be 131°C, 132°C, 133°C, 134°C, 135°C, 136°C, 137°C, 138°C or 139°C, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the said range.

[0078] Preferably, the refining time is 30-60 min, for example, it can be 32 min, 35 min, 38 min, 40 min, 42 min, 45 min, 48 min, 50 min, 52 min, 55 min or 58 min, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the said range.

[0079] Preferably, after the refining is completed, the temperature is lowered and then homogenized to obtain the grease body.

[0080] Preferably, the blending temperature is 90-110°C, for example, it can be 92°C, 95°C, 98°C, 100°C, 102°C, 105°C or 108°C, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0081] Preferably, the temperature at which the composite graphene and additives are added to the grease body is 90-110°C, for example, it can be 92°C, 95°C, 98°C, 100°C, 102°C, 105°C or 108°C, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0082] Preferably, the composite graphene is dispersed in base oil to prepare a modified graphene additive, and then the modified graphene additive is added to the grease body; thereby, the composite graphene can be better dispersed in the grease system.

[0083] Preferably, the mass percentage of composite graphene in the modified graphene additive is 0.1-10%, for example, it can be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% or 9%, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0084] Preferably, the blending further includes the steps of filtering, degassing and packaging.

[0085] In a third aspect, the present invention provides a use of the graphene lithium calcium-polyurea-based grease as described in the first aspect in mechanical equipment or automobiles.

[0086] In a fourth aspect, the present invention provides a device, which uses the graphene lithium calcium-polyurea grease as described in the first aspect.

[0087] Compared with the prior art, the present invention has the following beneficial effects:

[0088] (1) The graphene lithium calcium-polyurea-based grease provided by the present invention has excellent colloidal stability, mechanical stability, water resistance, and shear resistance, as well as excellent extreme pressure and wear resistance, high temperature resistance, and low temperature performance, by compounding the base oil with a calcium lithium-based thickener, a polyurea thickener, a composite graphene, and additives, thereby fully meeting the working conditions of the heavy machinery industry.

[0089] (2) Through component design and optimization, the present invention enables the graphene lithium calcium-polyurea-based grease to have an extremely low filling force at a low temperature of -15°C, with smooth filling, a friction coefficient of ≤0.19, and a dropping point of ≥182°C. It has significantly improved extreme pressure and wear resistance, high temperature resistance, and low temperature performance, and can meet the application requirements of heavy machinery under special working conditions such as high load, high temperature, high water content, and low temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0090] Figure 1 A process flow chart of the preparation method of graphene lithium calcium-polyurea grease provided in Example 1;

[0091] Figure 2 is a scanning electron microscope image of modified graphene oxide in a specific embodiment of the present invention;

[0092] Figure 3 This is a scanning electron microscope image of a three-dimensional graphene structure in a specific embodiment of the present invention;

[0093] Figure 4 TEM image of ionic liquid modified graphene in a specific embodiment of the present invention;

[0094] Figure 5 is a lattice diffraction pattern of ionic liquid-modified graphene in a specific embodiment of the present invention;

[0095] Figure 6 This is another transmission electron microscope image of ionic liquid-modified graphene in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0096] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0097] As used herein, the terms "comprises," "including," "having," "containing" or any other variations thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a listed element is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0098] "Optionally" or "either" means that the subsequently described event or circumstance can or cannot occur, and that the description includes instances where the event occurs and instances where it does not.

[0099] The indefinite articles "a" and "an" before the elements or components of the present invention do not limit the quantity requirement (i.e. the number of times they appear). Therefore, "a" or "an" should be interpreted as including one or at least one, and elements or components in the singular also include plural forms, unless the quantity clearly refers to only the singular form.

[0100] In the following specific embodiments of the present invention, the graphene materials involved are as follows:

[0101] 1. Modified graphene oxide: prepared using the preparation method disclosed in 201580002367.X;

[0102] The modified graphene oxide used in the following specific embodiments of the present invention is prepared by the above method, and its morphology is tested by scanning electron microscopy. The obtained scanning electron microscopy images are as follows: Figure 2 shown.

[0103] 2. Three-dimensional graphene structure is prepared by the following method:

[0104] Fumaric acid was added to deionized water and stirred vigorously at 80°C for a period of time. Then, 10 g of pretreated macroporous weakly acidic cation exchange resin was added and stirred for 8 hours. The mixture was then dried at 90°C for 12 hours to obtain a fumaric acid / ion exchange resin. KOH was then dissolved in deionized water. The dried fumaric acid / ion exchange resin was added to the KOH solution and stirred at 80°C for 6 hours. The mixture was then dried at 90°C for 48 hours, and the dried mixture was pulverized using a disintegrator. Finally, the mixture was heated at a rate of 5°C / min under a nitrogen stream, with heating at 750°C, 800°C, and 850°C for 2 hours, respectively. The mixture was then cooled to room temperature and stirred in a dilute HCl solution for 6 hours to remove any residual KOH. The mixture was then washed with water and alcohol multiple times to remove the HCl, and then dried at 60°C to obtain three-dimensional graphene.

[0105] The three-dimensional graphene used in the following specific embodiments of the present invention is prepared by the above method, and its morphology is tested by scanning electron microscopy. The obtained scanning electron microscope images are as follows: Figure 3 shown.

[0106] 3. Ionic liquid modified graphene, specifically 1-butyl-2-methylimidazolium tetrafluoroborate (ionic liquid LB104) modified graphene, was prepared according to the following method:

[0107] (1) Mix 10 mL of ionic liquid LB104 and 80 mL of deionized water in a beaker to obtain an electrolyte. Insert two high-purity graphite rods (99.9% purity) as cathode and anode vertically into the beaker and fix them close to the inner wall of the beaker to maintain a constant distance. Use wires to connect the two electrodes to a DC power supply to provide an operating voltage. Apply a voltage of 15 V, and the graphite rods begin to peel off layer by layer. Over time, the color of the electrolyte changes from light yellow to dark yellow, then to dark brown, and finally to a black solution with precipitates. The voltage is applied for 8 hours to obtain a modified graphene dispersion.

[0108] (2) The modified graphene dispersion obtained in step (1) was centrifuged at 6000 rpm for 10 min using a high-speed centrifuge, the precipitate was washed multiple times with anhydrous ethanol and deionized water, and dried in a vacuum drying oven at 40° C. to obtain ionic liquid-modified graphene.

[0109] The ionic liquid modified graphene used in the following specific embodiments of the present invention is prepared by the above method, and its morphology is tested by transmission electron microscopy. The transmission electron microscopy images obtained at different magnifications are as follows: Figure 4 and Figure 6 As shown, the lattice diffraction pattern is Figure 5 shown.

[0110] Example 1

[0111] A graphene lithium calcium-polyurea-based grease and a preparation method thereof, wherein the graphene lithium calcium-polyurea-based grease comprises the following components in parts by mass:

[0112]

[0113] Among them, the base oil is specifically composed of 26.5 parts of mineral oil A (Class I oil, bran full three-line oil), 17 parts of mineral oil B (paraffin-based base oil 250) and 44.5 parts of cycloalkyl base oil 4010; the calcium lithium-based thickener is composed of 2.5 parts of 12-hydroxy lithium stearate and 2.5 parts of 12-hydroxy calcium stearate; the polyurea thickener is a commercially available product purchased from Shandong Red Star Chemical Co., Ltd.; the composite graphene is composed of 0.01 parts of graphene A (modified graphene oxide) and 0.09 parts of graphene B (ionic liquid modified graphene); the extreme pressure and anti-wear agent is composed of 1.4 parts of extreme pressure agent A (boride, specifically inorganic borate), 1 part of extreme pressure agent B (sulfide, specifically sodium thiosulfate) and 0.5 parts of anti-wear agent (chlorinated paraffin); the adhesive is an OCP type tackifier purchased from Uni-President Lubricating Oil Company.

[0114] The process flow chart of the preparation method of the graphene lithium calcium-polyurea grease is as follows Figure 1 As shown, the details are as follows:

[0115] (1) lithium hydroxide monohydrate, calcium hydroxide and water are mixed in a mass ratio of 3:7 to prepare a saponifier solution; base oil, 12-hydroxystearic acid and the saponifier solution are added to a reaction device, and saponification reaction is carried out at 105° C. for 2 hours; after dehydration, a polyurea thickener is added thereto, compounded at 130° C. for 2 hours, and then refined at a high temperature of 135° C. for 50 minutes, then cooled and homogenized to obtain the grease body;

[0116] (2) The grease body is blended at 100° C., and additives such as composite graphene, extreme pressure anti-wear agent, adhesive, antioxidant, etc. are added to the grease body. After blending, degassing and packaging, the graphene lithium calcium-polyurea-based grease is obtained.

[0117] Examples 2-16, Comparative Examples 1-5

[0118] A graphene lithium calcium-polyurea-based grease differs from Example 1 only in the components and / or amounts of the graphene lithium calcium-polyurea-based grease, as shown in Tables 1, 2, and 3. The amounts of each component in Table 1 are all in parts, with "--" indicating that the component was not added. The preparation methods for each graphene lithium calcium-polyurea-based grease are the same as those in Example 1.

[0119] Table 1

[0120]

[0121]

[0122] Table 2

[0123]

[0124]

[0125] In Table 2, the composite graphene in Examples 10-16 is the same as the composite graphene in Example 9, which is a mixture of modified graphene oxide: ionic liquid modified graphene: three-dimensional structured graphene in a mass ratio of 8:1:1.

[0126] Table 3

[0127]

[0128]

[0129] Comparative Examples 9-10

[0130] Extreme pressure lithium-based grease, specifically the extreme pressure lithium-based grease (N type 2#) produced by China Petroleum Lubricants Company and the extreme pressure lithium-based grease (2#) produced by Shangling Lubricating Grease Co., Ltd.

[0131] The performance test of the grease provided in Examples 1-16 and Comparative Examples 1-10 was performed as follows:

[0132] 1. Basic performance

[0133] (1) Cone penetration: Test the working cone penetration of grease (0.1 mm) according to the method in GB / T 269-1991;

[0134] (2) Dropping point: Test the dropping point of grease according to the method in GB / T 4929 (°C);

[0135] (3) Stencil oil separation: The grease was separated from the stencil according to the method in NB / SH / T 0324 at 100°C for 24 h to obtain the mass fraction (%).

[0136] (4) Water loss: The water loss of grease was tested according to the method in standard SH / T 0109 at 38°C for 1 h, and the mass fraction (%) was obtained;

[0137] (5) Friction coefficient: The friction coefficient of grease was tested according to the method in standard SH / T 0202;

[0138] (6) Similar viscosity: Test the similar viscosity of grease according to the method in standard SH / T 0048 at -10℃ for 10s. -1 ;

[0139] (7) Four-ball extreme pressure and anti-wear test: Measure the PD value (N) of the grease according to the method in standard SH / T 0202;

[0140] (8) Four-ball test method for extreme pressure and anti-wear: The wear spot diameter (mm) of the grease is tested according to the method in standard SH / T 0202.

[0141] 2. Low temperature performance

[0142] (1) Difficulty of manual filling at low temperature

[0143] The grease to be tested was placed in a -20℃ low-temperature chamber and frozen for 16 hours. After that, it was taken out and a 2m pipe was installed at the outlet of the grease gun. The grease was added using a manual grease adding tool to observe the difficulty of manual grease filling.

[0144] The test results show that the graphene lithium calcium-polyurea-based grease provided in Example 9 of the present invention can be immediately loaded into a grease gun after being taken out, and the grease nozzle is connected to the pipeline and can be smoothly pumped out. The ease and smoothness of grease pumping are significantly higher than the extreme pressure lithium-based grease of Comparative Examples 9-10.

[0145] (2) Filling force test under low temperature environment

[0146] Loading mode: ① No-load filling 1, directly pumping out grease at a low temperature of -15°C; ② Whole machine filling, directly filling the large cavity pin shaft of the bucket cylinder of a 55-ton excavator at a low temperature of -15°C; ③ No-load filling 2, performing no-load filling 1 after filling the whole machine with grease at a low temperature of -15°C;

[0147] The grease is filled for 10 minutes at no load and with the whole machine, and the maximum value of each filling force during the grease filling process during this time period is recorded by a data acquisition instrument; the smaller the filling force, the better, which means that the grease is filled smoothly at low temperatures and has better low-temperature performance.

[0148] 3. Bench performance test

[0149] The test was conducted using a pin-shaft pendulum reciprocating tester. The greases to be tested were tested under the same experimental conditions for 30,000 runs (101.7 hours). The wear, friction coefficient, and temperature differences between the sleeve and shaft friction pairs exhibited by the greases to be tested were compared under the same running time.

[0150] The test materials include: bushing 95×80×80, pin 80×617, and the grease to be tested;

[0151] The test conditions are as follows: surface pressure: 500MPa; reciprocating time: 12.2s; swing angle: 100°; number of swings: 30,000 times; grease adding conditions: full of grease during assembly, no grease during the test; sleeve material and heat treatment conditions: 20CrMo / 20CrMnTi+carburizing and quenching; pin material and heat treatment conditions: 42CrMo+high-frequency quenching+surface chrome plating; sleeve and pin clearance: 0.15-0.20mm; test termination conditions: temperature > 100°C, friction coefficient > 0.30, abnormal noise or seizure, the number of swings reaches 30,000 times, if any of the conditions occurs, the test can be terminated.

[0152] The above performance test results are shown in Table 4 and Table 5.

[0153] Table 4

[0154]

[0155]

[0156] Table 5

[0157]

[0158]

[0159] According to the performance test results in Tables 4 and 5, the graphene lithium calcium-polyurea-based grease provided by the present invention has a working cone penetration of 271-279, a dropping point of 182-215°C, a steel mesh oil separation of 2.2-2.8%, a water runoff of 1.4-1.9%, a friction coefficient of 0.11-0.19, an extreme pressure and anti-wear PD value of 1960-2450 kgf, a wear spot diameter of 0.44-0.5 mm, and excellent colloidal stability, mechanical stability, water resistance, and shear resistance. It also has excellent extreme pressure and anti-wear properties, high temperature resistance, and low temperature performance. It can have a low filling force at a low temperature of -15°C, and the filling is smooth at low temperatures. In addition, it shows lower wear and temperature rise in bench comparison experiments, which fully meets the working conditions of the heavy machinery industry.

[0160] Specifically, in Examples 1-9 of the present invention, graphene lithium calcium-polyurea-based greases with different ratios of composite graphene were investigated. When graphene A: graphene B: graphene C were compounded at a ratio of 0.8:0.1:0.1, the three graphenes synergized with each other to optimize the grease performance. In Examples 10-13, graphene lithium calcium-polyurea-based greases with different ratios of composite graphene and extreme pressure anti-wear agents were investigated. When the composite graphene: extreme pressure agent A: extreme pressure agent B: anti-wear agent were compounded at a mass ratio of 2.97:0.01:0.01:0.01, the composite graphene and the extreme pressure anti-wear agent synergized with each other to optimize the grease performance. In Examples 14-16, calcium lithium-based thickeners and polyurea thickeners were formulated. When lithium 12-hydroxystearate: calcium 12-hydroxystearate: polyurea were compounded at a ratio of 6.7:0.5:0.5, the grease performance was optimal.

[0161] The greases in Comparative Examples 1-3 contain only one type of graphene, and the greases do not exhibit anti-wear advantages; in Comparative Examples 4-6, no graphene is added, but the amount of extreme pressure anti-wear agent is increased. In the bench comparison experiment, their anti-wear performance is poor and the temperature rise of the friction pair is high; the thickeners in Comparative Examples 7-8 do not adopt the compound of calcium-lithium-based thickener and polyurea thickener defined in the present invention, and the high-temperature performance of the grease is poor; Comparative Examples 9-10 are commercially available extreme pressure lithium-based greases. The grease performance indicators are normal, but the low-temperature filling force is significantly larger. In the bench comparison experiment, their friction and temperature rise are poor.

[0162] The applicant declares that while the above-described embodiments illustrate the graphene lithium calcium-polyurea grease, its preparation method, and its application, the present invention is not limited to the above-described process steps, nor does it necessarily rely on the above-described process steps for implementation. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the raw materials used, addition of auxiliary components, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A graphene lithium calcium-polyurea grease, characterized in that: The graphene lithium calcium-polyurea grease comprises the following components in parts by mass: The composite graphene includes a combination of at least two of modified graphene oxide, ionic liquid modified graphene, and three-dimensional structured graphene.

2. The graphene lithium calcium-polyurea grease according to claim 1, characterized in that The base oil includes any one of mineral base oil, synthetic base oil, and plant base oil, or a combination of at least two of them.

3. The graphene lithium calcium-polyurea grease according to claim 1 or 2, characterized in that: The calcium-lithium based thickener comprises a combination of 12-hydroxy lithium stearate and 12-hydroxy calcium stearate; The mass ratio of the 12-hydroxy lithium stearate to the 12-hydroxy calcium stearate is 1:(0.05-15).

4. The graphene lithium calcium-polyurea grease according to claim 1, characterized in that The mass percentage of modified graphene oxide in the composite graphene is 70-95%; The mass percentage of the ionic liquid modified graphene in the composite graphene is 5-15%; The mass percentage of the three-dimensional graphene in the composite graphene is 5-15%.

5. The graphene lithium calcium-polyurea grease according to claim 1, characterized in that: The ionic liquid in the ionic liquid modified graphene includes an imidazole ionic liquid; The imidazolium ionic liquid includes any one of 1-butyl-2-methylimidazolium tetrafluoroborate, 1-butyl-2-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-2,3-dimethylimidazolium tetrafluoroborate, and 1-butyl-2,3-dimethylimidazolium hexafluorophosphate, or a combination of at least two thereof; The ionic liquid modified graphene is prepared by the following method, which comprises: Performing electrochemical exfoliation using graphite as an electrode and an ionic liquid aqueous solution as an electrolyte to obtain a modified graphene dispersion; centrifuging the modified graphene dispersion to obtain the ionic liquid-modified graphene; The ionic liquid aqueous solution is an imidazole ionic liquid aqueous solution; The volume ratio of the ionic liquid to water in the ionic liquid aqueous solution is 1:(2-10).

6. The graphene lithium calcium-polyurea grease according to claim 1, characterized in that The additives include extreme pressure anti-wear agents, adhesives, preservatives, antioxidants and rust inhibitors; The graphene lithium calcium-polyurea-based grease further comprises 1-5 parts by mass of an extreme pressure anti-wear agent; The extreme pressure anti-wear agent includes any one of a boron extreme pressure anti-wear agent, a sulfide extreme pressure anti-wear agent, a phosphorus extreme pressure anti-wear agent, and a chloride extreme pressure anti-wear agent, or a combination of at least two thereof; The graphene lithium calcium-polyurea-based grease further comprises 0.1-1.5 parts by mass of an adhesive; The graphene lithium calcium-polyurea-based grease further comprises 0.1-1.5 parts by mass of a preservative; The graphene lithium calcium-polyurea grease further comprises 0.1-1.5 parts by mass of an antioxidant; The graphene lithium calcium-polyurea-based grease further comprises 0.1-1.5 parts by mass of a rust inhibitor.

7. A method for preparing the graphene lithium calcium-polyurea grease according to any one of claims 1 to 6, characterized in that: The preparation method comprises: preparing a grease body comprising a base oil, a calcium-lithium thickener, and a polyurea thickener; The composite graphene and additives are added to the grease body and blended to obtain the graphene lithium calcium-polyurea-based grease.

8. The method for preparing graphene lithium calcium-polyurea grease according to claim 7, characterized in that: The preparation method of the grease body comprises: mixing a base oil, 12-hydroxystearic acid and a saponifier solution, performing a saponification reaction, adding a polyurea thickener after dehydration, and then refining and homogenizing to obtain the grease body; the saponifier solution comprises a combination of lithium hydroxide, calcium hydroxide and water; The saponification reaction temperature is 90-120°C and the time is 1-3h; The compounding temperature is 120-140°C and the compounding time is 1-3 hours; The refining temperature is 130-140°C and the refining time is 30-60 minutes; After the refining is completed, the temperature is lowered and then homogenized to obtain the grease body.

9. The method for preparing graphene lithium calcium-polyurea grease according to claim 7 or 8, characterized in that: The blending temperature is 90-110°C; The temperature at which the composite graphene and additives are added to the grease body is 90-110° C.; The method further comprises the steps of filtering, degassing and subpackaging after the blending.

10. A device, characterized in that: The device uses the graphene lithium calcium-polyurea based grease as described in any one of claims 1 to 6.

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